Thiourethane-based optical material

ABSTRACT

A composition for making a high-refractive-index resin contains a polythiol compound and a compound containing at least two iso(thio)cyanato groups, the polythiol compound having a dithioacetal, dithioketal, orthotrithioformic ester, or orthotetrathiocarbonic ester skeleton. The molar ratio of the mercapto group to the iso(thio)cyanato group in the composition is greater than 1.0 but not more than 3.0. A method for making a resin by curing the composition, a resin prepared by curing the composition, an optical element made from the resin, and a lens made from the optical element are also provided.

TECHNICAL FIELD

The present invention relates to a resin for use in optical materials ofplastic lenses, prisms, optical fibers, information recording boards,filters, light-emitting diodes, or the like, to a polymerizablecomposition, i.e., the ingredient, of the resin, and to a mercaptocompound contained in the polymerizable composition. In particular, thepresent invention is suitable for application in spectacle lenses havinga high refractive index.

BACKGROUND ART

Plastic lenses, which are lightweight and unbreakable compared toinorganic lenses and can be dyed, are increasingly used in opticalelements such as spectacle lenses and camera lenses. Resins for makingplastic lenses are required to exhibit high performance, such as highrefractive index, high Abbe number, low specific gravity, high heatresistance, and the like. Various resin materials for making lenses havebeen developed and used to date. A representative example thereof is aplastic lens made from a polythiourethane resin (Japanese UnexaminedPatent Application Publication Nos. 60-199016, 62-267316, and 63-46213).A polythiourethane resin that exhibits higher refractive index due to anincreased sulfur content of thiol used in the polythiourethane has alsobeen developed (Japanese Unexamined Patent Application Publication Nos.2-270859 and 7-252207).

According to these methods, a high refractive index can be achievedwhile exhibiting a relatively high Abbe number; however, in order toobtain a polyurethane resin having a yet higher refractive index, anovel thiol having a high sulfur content or a novel polyisocyanatehaving a high sulfur content must be developed. Despite the need, thedevelopment of novel compounds is not easy. Moreover, in order for it tobe used in optical elements such as resins for making plastic lenses,physical properties, such as transparency, hue, heat resistance, andshock resistance, other than the refractive index must also be high.Development of a high-refractive-index urethane resin that satisfies allof these requirements is highly difficult.

In a typical conventional process of making a thiourethane resin bypolymerization of polythiol and polyiso(thio)cyanate, the polymerizablecomposition has been prepared such that the molar ratio of a mercaptogroup to an iso(thio)cyanato group is 1. No examples that investigatedthe molar ratio and the physical properties of the resin have existed.The reason for this is because when the molar ratio is made greater than1 using a conventional polythiol compound, i.e., when the mercapto groupis excessive relative to the iso(thio)cyanato group, the heat resistanceof the resin prepared by polymerization becomes dramatically poor, andthe resin may not be applied to optical elements such as plastic lenses.In general, however, high-sulfur-content compounds exhibit highrefractive index; hence, the refractive index of polythiol compounds isin most cases higher than that of polyiso(thio)cyanate. Accordingly, ifa thiourethane resin can be prepared by using an excessive amount ofpolythiol, which has a higher refractive index thanpolyiso(thio)cyanate, a resin with higher refractive index can be made.

Accordingly, an object of the present invention is to provide a methodfor easily obtaining a high-refractive-index resin.

DISCLOSURE OF INVENTION

The present inventors have conducted extensive investigations toovercome the above-described problems. As a result, the presentinventors have found that these problems can be overcome by using apolythiol compound characterized in having a dithioacetal, adithioketal, an orthotrithioformic ester, or an orthotetrathiocarbonicester skeleton in a molecule. In particular, the inventors have foundthat, in a polymerizable composition containing polyiso(thio)cyanate anda polythiol compound having a dithioacetal, dithioketal,orthotrithioformic ester, or orthotetrathiocarbonic ester skeleton in amolecule, a decrease in heat resistance of the resin can be minimizedand a resin with higher refractive index can be obtained by curing thepolymerizable composition whose molar ratio of mercapto toiso(thio)cyanato is greater than 1.0, i.e., the polymerizablecomposition containing an excessive amount of the mercapto grouprelative to the iso(thio)cyanato group. Thus, the inventors have madethe present invention based on these findings.

In particular, the features of the present invention are as follows.

[1] A polymerizable composition for making a high-refractive-indexresin, the composition containing a polythiol compound having adithioacetal, dithioketal, orthotrithioformic ester, ororthotetrathiocarbonic ester skeleton, and at least two mercapto groups;and a compound having at least two iso(thio)cyanato groups, wherein themolar ratio of the mercapto group to the iso(thio)cyanato group isgreater than 1.0 but not more than 3.0.

[2] The polymerizable composition according to [1] wherein the polythiolcompound has a mercaptomethylthio group.

[3] The polymerizable composition according to [1] or [2], wherein thepolythiol compound having the dithioketal or dithioacetal skeleton isrepresented by General Formula (1)

(wherein R¹ is an aliphatic residue, a heterocyclic residue, or anaromatic residue with a valence of n; R² is a hydrogen atom, analiphatic residue, a heterocyclic residue, or an aromatic residue with avalence of 1; and R³ and R⁴ are each independently an aliphatic residue,a heterocyclic residue, or an aromatic residue with a valence of 1, andR³ and R⁴ may bond to each other to form a ring or each may bond to R³or R⁴ in another set of parentheses to form a ring when n is 2 or more;wherein at least one of R¹, R², R³, and R⁴ must have at least onemercapto group, and m1+(m2+m3+m4)×n≧2, wherein m1, m2, m3, and m4represent the numbers of mercapto group contained in R¹, R², R³, and R⁴,respectively; wherein n is an integer of 1 or more.)

[4] The polymerizable composition according to [3], wherein R² inGeneral Formula (1) is a hydrogen atom.

[5] The polymerizable composition according to [4], wherein thepolythiol compound having the dithioacetal skeleton is at least oneselected from the group consisting of1,1,3,3-tetrakis(mercaptomethylthio)propane,1,1,2,2-tetrakis(mercaptomethylthio)ethane,4,6-bis(mercaptomethylthio)-1,3-dithiane, and2-(2,2-bis(mercaptomethylthio)ethyl)-1,3-dithietane.

[6] The polymerizable composition according to [1] or [2], wherein thepolythiol compound having the orthotrithioformic ester skeleton isrepresented by General Formula (2)

(wherein R⁵ is an aliphatic residue, a heterocyclic residue, or anaromatic residue with a valence of p, and R⁶ and R⁷ are eachindependently an aliphatic residue, a heterocyclic residue, or anaromatic residue with a valence of 1 and may bond to each other to forma ring; wherein at least one of R⁵, R⁶ and R⁷ must have at least onemercapto group, and m5+(m6+m7)×p≧2, wherein m5, m6, and m7 represent thenumbers of mercapto group contained in R⁵, R⁶, and R⁷, respectively; andwherein p is an integer of 1 or more.)

[7] The polymerizable composition according to [6], wherein R⁶ and R⁷are each a mercaptomethyl group.

[8] The polymerizable composition according to [7], wherein thepolythiol compound represented by General Formula (2) is at least oneselected from the group consisting of tris(mercaptomethylthio)methane,1,1,5,5-tetrakis(mercaptomethylthio)-2,4-dithiapentane, andbis(4,4-bis(mercaptomethylthio)-1,3-dithiabutyl)(mercaptomethylthio)methane.

[9] The polymerizable composition according to [1] or [2], containingthe polythiol compound having the orthotetrathiocarbonic ester skeletonrepresented by General Formula (3)

(wherein R⁸, R⁹, R¹⁰, and R¹¹ are each independently an aliphaticresidue, a heterocyclic residue, or an aromatic residue and may eachbond with one of other residues to form a ring; wherein at least one ofR⁸, R⁹, R¹⁰, and R¹¹ must contain at least one mercapto group, andm8+m9+m10+m11≧2, wherein m8, m9, m10, and m11 represent the numbers ofmercapto group in R⁸, R⁹, R¹⁰, and R¹¹, respectively.)

[10] A method for making a resin by curing the polymerizable compositionaccording to any one of [1] to [9].

[11] A resin prepared by curing the polymerizable composition accordingto any one of [1] to [9].

[12] An optical element comprising the resin according to [11].

[13] A lens comprising the optical element according to [12].

[14] 4,6-bis(mercaptomethylthio)-1,3-dithiane. [15]2-(2,2-bis(mercaptomethylthio)ethyl)-1,3-dithietane.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will now be described in detail.

In the invention, the excess rate of the polythiol compound isdetermined ad libitum. In preparing a polymerizable composition,polythiol and polyiso(thio)cyanato are prepared so that the molar ratioof the mercapto group to the iso(thio)cyanato group is greater than 1.0but not more than 3.0.

The polymerizable composition of the invention is characterized in thatthe mercapto group is excessive relative to the iso(thio)cyanato groupin the composition. In other words, the molar ratio (SH/NCO) of themercapto group to the isocyanato group is adjusted to be greater than1.0. In this manner, a resin exhibiting a higher refractive indexcompared to when the molar ratio is 1.0 can be obtained. On the otherhand, the upper limit of the molar ratio depends on the heat resistanceof the resin cured at a molar ratio of 1.0; however, the cured productexhibits satisfactory heat resistance when the molar ratio is not morethan 3.0.

In the present invention, the molar ratio of the mercapto group to theisocyanato group is 1.0<(SH/NCO)≦3.0, preferably, 1.01<(SH/NCO)≦3.0,more preferably 1.01<(SH/NCO)≦2.0, and most preferably1.05<(SH/NCO)<1.3.

The polythiol compound of the present invention has a dithioacetal,dithioketal, orthotrithioformic ester, or orthotetrathiocarbonic esterpolythiol skeleton. No particular limit is imposed as long as thepolythiol has any of these skeletons. For example, the polythiol havingthe dithioacetal or dithioketal skeleton can be represented by GeneralFormula (1):

Here, R¹ is an aliphatic residue, a heterocyclic residue, or an aromaticresidue with a valence of n; R² is a hydrogen atom, an aliphaticresidue, a heterocyclic residue, or an aromatic residue with a valenceof 1; and R³ and R⁴ are each independently an aliphatic residue, aheterocyclic residue, or an aromatic residue with a valence of 1, and R³and R⁴ may bond to each other to form a ring or each may bond to R³ orR⁴ in another set of parentheses to form a ring when n is 2 or more. Atleast one of R¹, R², R³, and R⁴ must have at least one mercapto group,and m1+(m2+m3+m4)×n>2, wherein m1, m2, m3, and m4 represent the numbersof mercapto group contained in R¹, R², R³, and R⁴, respectively, and nis an integer of 1 or more.

R¹ may be any as long as R¹ is an organic residue having a valence of nderived from aliphatic, heterocyclic, or aromatic. Preferably, thenumber of carbon atoms is in the range of 1 to 15. Examples thereofinclude organic residues having a valence of n derived fromstraight-chain aliphatic groups such as methane, ethane, propane,butane, pentane, hexane, ethylene, propylene, 1-butene, 2-butene,butadiene, and the like; organic residues having a valence of n derivedfrom cyclic fatty series such as cyclopentane, cyclopentene,cyclopentadiene, cyclohexane, 1,2-dimethylcyclohexane,1,3-dimethylcyclohexane, 1,4-dimethylcyclohexane, cyclohexene,1,3-cyclohexadiene, 1,4-cyclohexadiene, norbornane,2,3-dimethylnorbornane, 2,5-dimethylnorbornane, 2,6-dimethylnorbornane,bis(4-methylcyclohexyl)methane, and the like;

-   -   organic residues having a valence of n derived from heterocycles        such as thiolane, 2,5-dimethylthiolane, 3,4-dimethylthiolane,        2,3-dimethylthiolane, 2,4-dimethylthiolane, 2,5-diethylthiolane,        3,4-diethylthiolane, 2,3-diethylthiolane, 1,3-dithiolene,        2,4-dimethyl-1,3-dithiolene, 4,5-dimethyl-1,3-dithiolene,        2,4-diethyl-1,3-dithiolene, 4,5-diethyl-1,3-dithiolene,        1,3-dithiolane, 2,4-dimethyl-1,3-dithiolane,        4,5-dimethyl-1,3-dithiolane, 2,4-diethyl-1,3-dithiolane,        4,5-diethyl-1,3-dithiolane, thiophene, 2,5-dimethylthiophene,        1,4-dithiane, 2,5-dimethyl-1,4-dithiane,        2,6-dimethyl-1,4-dithiane, 2,3-dimethyl-1,4-dithiane,        2,5-diethyl-1,4-dithiane, 2,6-diethyl-1,4-dithiane,        2,3-diethyl-1,4-dithiane, 1,3,5-trithiane,        2,4-dimethyl-1,3,5-trithiane, 2,4-diethyl-1,3,5-trithiane,        thiazole, 1,3,4-thiadiazole, 1,3-dithietane,        2,4-dimethyl-1,3-dithietane, 2,4-diethyl-1,3-dithietane, and the        like;    -   organic residues having a valence of n derived from aromatic        series such as benzene, o-xylene, m-xylene, p-xylene,        naphthalene, biphenyl, anthracene, perylene, styrene,        ethylbenzene, and the like; and organic groups having a valence        of n formed by removing mercapto groups from conventional thiol        compounds.

Examples of the conventional thiol compounds include monofunctionalthiols such as methanethiol, ethanethiol, 2-mercaptoethyl-1,3-dithiane,thiophenol, and benzylthiol; aliphatic polythiol compounds such asmethanedithiol, 1,2-ethanedithiol, 1,1-propanedithiol,1,2-propanedithiol, 1,3-propanedithiol, 2,2-propanedithiol,1,6-hexanedithiol, 1,2,3-propanetrithiol, 1,1-cyclohexanedithiol,1,2-cyclohexanedithiol, 2,2-dimethylpropane-1,3-dithiol,3,4-dimethoxybutane-1,2-dithiol, 2-methylcyclohexane-2,3-dithiol,1,1-bis(mercaptomethyl)cyclohexane, bis(2-mercaptoethyl) thiomalate,2,3-dimercapto-1-propanol(2-mercaptoacetate),2,3-dimercapto-1-propanol(3-mercaptopropionate), diethylene glycolbis(2-mercaptoacetate), diethylene glycol bis(3-mercaptopropionate),1,2-dimercapto propyl methyl ether, 2,3-dimercapto propyl methyl ether,2,2-bis(mercaptomethyl)-1,3-propanedithiol, bis(2-mercaptoethyl)ether,ethylene glycol bis(2-mercaptoacetate), ethylene glycolbis(3-mercaptopropionate), trimethylol propane bis(2-mercaptoacetate),trimethylol propane bis(3-mercaptopropionate), pentaerythritoltetrakis(2-mercaptoacetate), pentaerythritoltetrakis(3-mercaptopropionate), and tetrakis(mercaptomethyl)methane;

-   -   aromatic polythiols such as 1,2-dimercaptobenzene,        1,3-dimercaptobenzene, 1,4-dimercaptobenzene,        1,2-bis(mercaptomethyl)benzene, 1,3-bis(mercaptomethyl)benzene,        1,4-bis(mercaptomethyl)benzene, 1,2-bis(mercaptoethyl)benzene,        1,3-bis(mercaptoethyl)benzene, 1,4-bis(mercaptoethyl)benzene,        1,2,3-trimercaptobenzene, 1,2,4-trimercaptobenzene,        1,3,5-trimercaptobenzene, 1,2,3-tris(mercaptomethyl)benzene,        1,2,4-tris(mercaptomethyl)benzene,        1,3,5-tris(mercaptomethyl)benzene,        1,2,3-tris(mercaptoethyl)benzene,        1,2,4-tris(mercaptoethyl)benzene,        1,3,5-tris(mercaptoethyl)benzene, 2,5-toluenedithiol,        3,4-toluenedithiol, 1,3-di(p-methoxyphenyl)propane-2,2-dithiol,        1,3-diphenylpropane-2,2-dithiol, phenylmethane-1,1-dithiol, and        2,4-di(p-mercaptophenyl)pentane;    -   aromatic polythiol compounds containing sulfur atoms other than        in the mercapto groups such as        1,2-bis(mercaptoethylthio)benzene,        1,3-bis(mercaptoethylthio)benzene,        1,4-bis(mercaptoethylthio)benzene,        1,2,3-tris(mercaptomethylthio)benzene,        1,2,4-tris(mercaptomethylthio)benzene,        1,3,5-tris(mercaptomethylthio)benzene,        1,2,3-tris(mercaptoethylthio)benzene,        1,2,4-tris(mercaptoethylthio)benzene, and        1,3,5-tris(mercaptoethylthio)benzene, and ring-alkylated        derivatives of these;    -   bis(mercaptomethyl)sulfide, bis(mercaptomethyl) disulfide,        bis(mercaptoethyl)sulfide, bis(mercaptoethyl) disulfide,        bis(mercaptopropyl)sulfide, bis(mercaptomethylthio)methane,        bis(2-mercaptoethylthio) methane,        bis(3-mercaptopropylthio)methane,        1,2-bis(mercaptomethylthio)ethane,        1,2-bis(2-mercaptoethylthio)ethane,        1,2-bis(3-mercaptopropyl)ethane,        1,3-bis(mercaptomethylthio)propane,        1,3-bis(2-mercaptoethylthio)propane,        1,3-bis(3-mercaptopropylthio)propane,        1,2,3-tris(mercaptomethylthio)propane,        1,2,3-tris(2-mercaptoethylthio)propane,        1,2,3-tris(3-mercaptopropylthio)propane,        1,2-bis[(2-mercaptoethyl)thio]-3-mercaptopropane,        4,8-dimercaptomethyl-1,11-mercapto-3,6,9-trithiaundecane,        4,7-dimercaptomethyl-1,11-mercapto-3,6,9-trithiaundecane,        5,7-dimercaptomethyl-1,11-mercapto-3,6,9-trithiaundecane,        tetrakis(mercaptomethylthiomethyl)methane,        tetrakis(2-mercaptoethylthiomethyl)methane,        tetrakis(3-mercaptopropylthiomethyl)methane,        bis(2,3-dimercaptopropyl) sulfide,        bis(1,3-dimercaptopropyl)sulfide, 2,5-dimercapto-1,4-dithiane,        2,5-dimercaptomethyl-1,4-dithiane,        2,5-dimercaptomethyl-2,5-dimethyl-1,4-dithiane,        bis(mercaptomethyl)disulfide, bis(mercaptoethyl)disulfide, and        bis(mercaptopropyl)disulfide, and esters of thioglycolates and        mercaptopropionates of these;    -   aliphatic polythiol compounds containing sulfur atoms other than        in the mercapto groups, such as hydroxymethyl sulfide        bis(2-mercaptoacetate), hydroxymethyl sulfide        bis(3-mercaptopropionate), hydroxyethyl sulfide        bis(2-mercaptoacetate), hydroxyethyl sulfide        bis(3-mercaptopropionate), hydroxypropyl sulfide        bis(2-mercaptoacetate), hydroxypropyl sulfide        bis(3-mercaptopropionate), hydroxymethyl disulfide        bis(2-mercaptoacetate), hydroxymethyl disulfide        bis(3-mercaptopropionate), hydroxyethyl disulfide        bis(2-mercaptoacetate), hydroxyethyl disulfide        bis(3-mercaptopropionate), hydroxypropyl disulfide        bis(2-mercaptoacetate), hydroxypropyl disulfide        bis(3-mercaptopropionate), 2-mercaptoethylether        bis(2-mercaptoacetate), 2-mercaptoethylether        bis(3-mercaptopropionate), 1,4-dithiane-2,5-diol        bis(2-mercaptoacetate), 1,4-dithiane-2,5-diol        bis(3-mercaptopropionate), bis(2-mercaptoethyl)thiodiglycolate,        bis(2-mercaptoethyl)thiodipropionate, bis(2-mercaptoethyl)        4,4-thiodibutylate, bis(2-mercaptoethyl) dithiodiglycolate,        bis(2-mercaptoethyl) dithiodipropionate, bis(2-mercaptoethyl)        4,4-dithiodibutylate, bis(2,3-dimercaptopropyl)thiodiglycolate,        bis(2,3-dimercaptopropyl) thiodipropionate,        bis(2,3-dimercaptopropyl) dithioglycolate, and        bis(2,3-dimercaptopropyl) dithiodipropionate;    -   heterocyclic compounds containing sulfur atoms other than in the        mercapto groups, such as 3,4-thiophenedithiol and        2,5-dimercapto-1,3,4-thiadiazole; and compounds containing        hydroxyl groups in addition to the mercapto groups, such as        2-mercaptoethanol, 3-mercapto-1,2-propanediol, glycerin        di(mercaptoacetate), 1-hydroxy-4-mercaptocyclohexane,        2,4-dimercaptophenol, 2-mercaptohydroquinone, 4-mercaptophenol,        3,4-dimercapto-2-propanol, 1,3-dimercapto-2-propanol,        2,3-dimercapto-1-propanol, 1,2-dimercapto-1,3-butanediol,        pentaerythritol tris(3-mercaptopropionate), pentaerythritol        mono(3-mercaptopropionate), pentaerythritol        bis(3-mercaptopropionate), pentaerythritol tris(thioglycolate),        dipentaerythritol pentakis(3-mercaptopropionate),        hydroxymethyl-tris(mercaptoethylthiomethyl)methane, and        1-hydroxyethylthio-3-mercaptoethylthiobenzene.

Examples of the monovalent aliphatic residue, heterocyclic residue, andaromatic residue in R², R³, and R⁴ include monovalent organic residuesderived from examples of straight-chain aliphatic series, cyclicaliphatic series, heterocycles, and aromatic series described in R¹; andorganic residues obtained by removing mercapto groups from theabove-described thiol compounds. When R³ and R⁴ bond to each other toform a ring, examples of the ring that contains a dithioacetal structureinclude four- to eight-membered rings, such as 1,3-dithiacyclobutane,1,3-dithiacyclopentane, 1,3-dithiacyclohexane, 1,3-dithiacycloheptane,and the like. Moreover, when n is 2 or more, (R³)s in different sets ofparentheses bond to form a ring. For example,4,6-bis(mercaptomethylthio)-1,3-dithiacyclohexane is included in theexample.

n may be any integer as long as n is not less than 1. Sincepurification, handling, or the like becomes difficult as n increases, nis preferably an integer between 1 and 4.

Specific examples of the compound represented by Formula (1) include1,1,3,3-tetrakis(mercaptomethylthio)propane,1,1,2,2-tetrakis(mercaptomethylthio)ethane,4,6-bis(mercaptomethylthio)-1,3-dithiacyclohexane,1,1,5,5-tetrakis(mercaptomethylthio)-3-thiapentane,1,1,6,6-tetrakis(mercaptomethylthio)-3,4-dithiahexane,2,2-bis(mercaptomethylthio)ethanethiol,2-(4,5-dimercapto-2-thiapentyl)-1,3-dithiacyclopentane,2,2-bis(mercaptomethyl)-1,3-dithiacyclopentane,2,5-bis(4,4-bis(mercaptomethylthio)-2-thiabutyl)-1,4-dithiane,2,2-bis(mercaptomethylthio)-1,3-propanedithiol,3-mercaptomethylthio-1,7-dimercapto-2,6-dithiaheptane,3,6-bis(mercaptomethylthio)-1,9-dimercapto-2,5,8-trithianonane,4,6-bis(mercaptomethylthio)-1,9-dimercapto-2,5,8-trithianonane,3-mercaptomethylthio-1,6-dimercapto-2,5-dithiahexane,2-(2,2-bis(mercaptomethylthio)ethyl)-1,3-dithietane,1,1,9,9-tetrakis(mercaptomethylthio)-5-(3,3-bis(mercaptomethylthio)-1-thiapropyl)3,7-dithianonane,tris(2,2-bis(mercaptomethylthio)ethyl)methane,tris(4,4-bis(mercaptomethylthio)-2-thiabutyl)methane,tetrakis(2,2-bis(mercaptomethylthio)ethyl)methane,tetrakis(4,4-bis(mercaptomethylthio)-2-thiabutyl)methane,3,5,9,11-tetrakis(mercaptomethylthio)-1,13-dimercapto-2,6,8,12-tetrathiatridecane,3,5,9,11,15,17-hexakis(mercaptomethylthio)-1,19-dimercapto-2,6,8,12,14,18-hexathianonadecane,9-(2,2-bis(mercaptomethylthio)ethyl)-3,5,13,15-tetrakis(mercaptomethylthio)-1,17-dimercapto-2,6,8,10,12,16-hexathiaheptadecane,3,4,8,9-tetrakis(mercaptomethylthio)-1,11-dimercapto-2,5,7,10-tetrathiaundecane,3,4,8,9,13,14-hexakis(mercaptomethylthio)-1,16-dimercapto-2,5,7,10,12,15-hexathiahexadecane,8-{bis(mercaptomethylthio)methyl}-3,4,12,13-tetrakis(mercaptomethylthio)-1,15-dimercapto-2,5,7,9,11,14-hexathiapentadecane,4,6-bis{3,5-bis(mercaptomethylthio)-7-mercapto-2,6-dithiaheptylthio}-1,3-dithiane,4-{3,5-bis(mercaptomethylthio)-7-mercapto-2,6-dithiaheptylthio}-6-mercaptomethylthio-1,3-dithiane,1,1-bis{4-(6-mercaptomethylthio)-1,3-dithianylthio}-3,3-bis(mercaptomethylthio)propane,1,3-bis{4-(6-mercaptomethylthio)-1,3-dithianylthio}-1,3-bis(mercaptomethylthio)propane,1-{4-(6-mercaptomethylthio)-1,3-dithianylthio}-3-{2,2-bis(mercaptomethylthio)ethyl}-7,9-bis(mercaptomethylthio)-2,4,6,10-tetrathiaundecane,1-{4-(6-mercaptomethylthio)-1,3-dithianylthio}-3-{2-(1,3-dithietanyl)}methyl-7,9-bis(mercaptomethylthio)-2,4,6,10-tetrathiaundecane,1,5-bis{4-(6-mercaptomethylthio)-1,3-dithianylthio}-3-{2-(1,3-dithietanyl)}methyl-2,4-dithiapentane,4,6-bis[3-{2-(1,3-dithietanyl)}methyl-5-mercapto-2,4-dithiapentylthio]-1,3-dithiane,4,6-bis{4-(6-mercaptomethylthio)-1,3-dithianylthio}-1,3-dithiane,4-{4-(6-mercaptomethylthio)-1,3-dithianylthio}-6-{4-(6-mercaptomethylthio)-1,3-dithianylthio}-1,3-dithiane,3-{2-(1,3-dithietanyl)}methyl-7,9-bis(mercaptomethylthio)-1,11-dimercapto-2,4,6,10-tetrathiaundecane,9-{2-(1,3-dithietanyl)}methyl-3,5,13,15-tetrakis(mercaptomethylthio)-1,17-dimercapto-2,6,8,10,12,16-hexathiaheptadecane,3-{2-(1,3-dithietanyl)}methyl-7,9,13,15-tetrakis(mercaptomethylthio)-1,17-dimercapto-2,4,6,10,12,16-hexathiaheptadecane,3,7-bis{2-(1,3-dithietanyl)}methyl-1,9-dimercapto-2,4,6,8-tetrathianonane,4-{3,4,8,9-tetrakis(mercaptomethylthio)-11-mercapto-2,5,7,10-tetrathiaundecyl}-5-mercaptomethylthio-1,3-dithiolane,4,5-bis{3,4-bis(mercaptomethylthio)-6-mercapto-2,5-dithiahexylthio}-1,3-dithiolane,4-{3,4-bis(mercaptomethylthio)-6-mercapto-2,5-dithiahexylthio}-5-mercaptomethylthio-1,3-dithiolane,4-{3-bis(mercaptomethylthio)methyl-5,6-bis(mercaptomethylthio)-8-mercapto-2,4,7-trithiaoctyl}-5-mercaptomethylthio-1,3-dithiolane,2-[bis{3,4-bis(mercaptomethylthio)-6-mercapto-2,5-dithiahexylthio}methyl]-1,3-dithietane,2-{3,4-bis(mercaptomethylthio)-6-mercapto-2,5-dithiahexylthio}mercaptomethylthiomethyl-1,3-dithietane,2-{3,4,8,9-tetrakis(mercaptomethylthio)-1′-mercapto-2,5,7,10-tetrathiaundecylthio}mercaptomethylthiomethyl-1,3-dithietane,2-{3-bis(mercaptomethylthio)methyl-5,6-bis(mercaptomethylthio)-8-mercapto-2,4,7-trithiaoctyl}mercaptomethylthiomethyl-1,3-dithietane,4,5-bis[1-{2-(1,3-dithietanyl)}-3-mercapto-2-thiapropylthio]-1,3-dithiolane,4-[1-{2-(1,3-dithietanyl)}-3-mercapto-2-thiapropylthio]-5-{1,2-bis(mercaptomethylthio)-4-mercapto-3-thiabutylthio}-1,3-dithiolane,2-[bis{4-(5-mercaptomethylthio-1,3-dithiolanyl)thio}]methyl-1,3-dithietane,4-{4-(5-mercaptomethylthio-1,3-dithiolanyl)thio}-5-[1-{2-(1,3-dithietanyl)}-3-mercapto-2-thiapropylthio]-1,3-dithiolane,and the like. These examples are no limiting. Polymer compounds thathave no particular repeated structure but have the dithioacetal ordithioketal skeleton and at least two mercapto groups may also be used.

The polythiol compound having the orthotrithioformic ester skeleton isnot particularly limited. An example is a compound represented byGeneral Formula (2)

Here, R⁵ is an aliphatic residue, a heterocyclic residue, or an aromaticresidue with a valence of p; R⁶ and R⁷ are each independently analiphatic residue, a heterocyclic residue, or an aromatic residue with avalence of 1, and R⁶ and R⁷ may bond to each other to form a ring. Atleast one of R⁵, R⁶ and R⁷ must have at least one mercapto group, andm5+(m6+m7)×p≧2, wherein m5, m6, and m7 represent the numbers of mercaptogroup contained in R⁵, R⁶, and R⁷, respectively, and p is an integer of1 or more.

R⁵ is not particularly limited as long as R⁵ is any organic residuehaving a valence of p derived from aliphatic series, heterocycles, oraromatic series. Preferably, R⁵ is an organic residue having a valenceof p derived from any of examples of straight-chain aliphatic series,cyclic aliphatic series, heterocycles, and aromatic series described inR¹ of Formula (1) or an organic residue having a valence of p obtainedby removing the mercapto group from the above-described conventionalthiol compound. R⁶ and R⁷ are not particularly limited as long as theyare each a monovalent organic residue derived from any of theabove-described examples of aliphatic series, heterocycles, and aromaticseries. Preferably, as with R³ and R⁴ in Formula (1), R⁶ and R⁷ are eachan organic residue obtained by removing the mercapto group from theknown thiol compound and may form a ring. p may be any integer not lessthan 1. As with n, p is preferably an integer in the range of 1 to 4.

Specific examples of the polythiol compound having theorthotrithioformic ester skeleton represented by Formula (2) includetris(mercaptomethylthio)methane, tris(mercaptoethylthio)methane,1,1,5,5-tetrakis(mercaptomethylthio)-2,4-dithiapentane,bis(4,4-bis(mercaptomethylthio)-1,3-dithiabutyl)(mercaptomethylthio)methane,tris(4,4-bis(mercaptomethylthio)-1,3-dithiabutyl)methane,2,4,6-tris(mercaptomethylthio)-1,3,5-trithiacyclohexane,2,4-bis(mercaptomethylthio)-1,3,5-trithiacyclohexane,1,1,3,3-tetrakis(mercaptomethylthio)-2-thiapropane,bis(mercaptomethyl)methylthio-1,3,5-trithiacyclohexane,tris((4-mercaptomethyl-2,5-dithiacyclohexyl-1-yl)methylthio)methane,2,4-bis(mercaptomethylthio)-1,3-dithiacyclopentane,2-mercaptoethylthio-4-mercaptomethyl-1,3-dithiacyclopentane,2-(2,3-dimercaptopropylthio)-1,3-dithiacyclopentane,4-mercaptomethyl-2-(2,3-dimercaptopropylthio)-1,3-dithiacyclopentane,4-mercaptomethyl-2-(1,3-dimercapto-2-propylthio)-1,3-dithiacyclopentane,tris(2,2-bis(mercaptomethylthio)-1-thiaethyl)methane,tris(3,3-bis(mercaptomethylthio)-2-thiapropyl)methane,tris(4,4-bis(mercaptomethylthio)-3-thiabutyl)methane,2,4,6-tris(3,3-bis(mercaptomethylthio)-2-thiapropyl)-1,3,5-trithiacyclohexane,tetrakis(3,3-bis(mercaptomethylthio)-2-thiapropyl)methane, and oligomersof these. These examples are no limiting. Moreover, polymers that do nothave a particular repeated structure can be used as long as thesepolymers have the trithioorthoformic ester skeleton and at least twomercapto groups.

The polythiol compound having the tetrathioorthocarbonic ester skeletonis not particularly limited. An example is a compound represented byGeneral Formula (3)

Here, R⁸, R⁹, R¹⁰, and R¹¹ are each independently an aliphatic residue,a heterocyclic residue, or an aromatic residue and may each bond withone of other residues to form a ring. At least one of R⁸, R⁹, R¹⁰, andR¹¹ must contain at least one mercapto group, and m8+m9+m10+m11≧2,wherein m8, m9, m10, and m11 represent the numbers of mercapto group inR⁸, R⁹, R¹⁰, and R¹¹, respectively.

R⁸, R⁹, R¹⁰, and R¹¹ are not particularly limited as long as they arealiphatic residues, heterocyclic residues, or aromatic residues. As withR³ and R⁴ in Formula (1), each of R⁸, R⁹, R¹⁰, and R¹¹ is preferably anorganic residue obtained by removing a mercapto group from a known thiolcompound and may form a ring as with R³ and R⁴.

Specific examples of the polythiol compound having thetetrathioorthocarbonic ester skeleton represented by Formula (3) include3,3′-di(mercaptomethylthio)-1,5-dimercapto-2,4-dithiapentane,2,2′-di(mercaptomethylthio)-1,3-dithiacyclopentane,2,7-di(mercaptomethyl)-1,4,5,9-tetrathiaspiro[4,4]nonane, and3,9-dimercapto-1,5,7,11-tetrathiaspiro[5,5]undecane. These examples areno limiting. The polythiol compound may be a polymer having noparticular repeated structure as long as the polymer has thetetrathiocarbonic ester skeleton and at least two mercapto groups.

The polythiol compound of the present invention is characterized byhaving a dithioacetal, dithioketal, orthotrithioformic ester, ororthotetrathiocarbonic ester skeleton in the molecule. Preferably, thepolythiol compound additionally contains a mercaptomethylthio group toachieve yet higher refractive index and maintain heat resistance.

The polymerizable composition of the present invention is characterizedby containing the above-described polythiol compound. The polythiolcompounds described above may be used alone or in combination.

Moreover, other thiol compounds may be used in addition, if necessary.

Examples of other thiol compounds include aliphatic polythiol compoundssuch as methanedithiol, ethanedithiol, 1,1-propanedithiol,1,2-propanedithiol, 1,3-propanedithiol, 1,6-hexanedithiol,1,2,3-propanetrithiol, 1,1-cyclohexanedithiol, 1,2-cyclohexanedithiol,2,2-dimethylpropane-1,3-dithiol, 3,4-dimethoxybutane-1,2-dithiol,2-methylcyclohexane-2,3-dithiol, 1,1-bis(mercaptomethyl)cyclohexane,bis(2-mercaptoethyl) thiomalate,2,3-dimercapto-1-propanol(2-mercaptoacetate),2,3-dimercapto-1-propanol(3-mercaptopropionate), diethylene glycolbis(2-mercaptoacetate), diethylene glycol bis(3mercaptopropionate),1,2-dimercapto propyl methyl ether, 3-dimercapto propyl methyl ether,2,2-bis(mercaptomethyl)-1,3-propanedithiol, bis(2-mercaptoethyl)ether,ethylene glycol bis(2-mercaptoacetate), ethylene glycolbis(3-mercaptopropionate), trimethylol propane bis(2-mercaptoacetate),trimethylol propane bis(3-mercaptopropionate), pentaerythritoltetrakis(2-mercaptoacetate), pentaerythritoltetrakis(3-mercaptopropionate), and tetrakis(mercaptomethyl)methane;

-   -   aromatic polythiols such as 1,2-dimercaptobenzene,        1,3-dimercaptobenzene, 1,4-dimercaptobenzene,        1,2-bis(mercaptomethyl)benzene, 1,3-bis(mercaptomethyl)benzene,        1,4-bis(mercaptomethyl)benzene, 1,2-bis(mercaptoethyl)benzene,        1,3-bis(mercaptoethyl)benzene, 1,4-bis(mercaptoethyl)benzene,        1,2,3-trimercaptobenzene, 1,2,4-trimercaptobenzene,        1,3,5-trimercaptobenzene, 1,2,3-tris(mercaptomethyl)benzene,        1,2,4-tris(mercaptomethyl)benzene,        1,3,5-tris(mercaptomethyl)benzene,        1,2,3-tris(mercaptoethyl)benzene,        1,2,4-tris(mercaptoethyl)benzene,        1,3,5-tris(mercaptoethyl)benzene, 2,5-toluenedithiol,        3,4-toluenedithiol, 1,3-di(p-methoxyphenyl)propane-2,2-dithiol,        1,3-diphenylpropane-2,2-dithiol, phenylmethane-1,1-dithiol, and        2,4-di(p-mercaptophenyl)pentane;    -   aromatic polythiol compounds containing a sulfur atom other than        in the mercapto group, such as        1,2-bis(mercaptoethylthio)benzene,        1,3-bis(mercaptoethylthio)benzene,        1,4-bis(mercaptoethylthio)benzene,        1,2,3-tris(mercaptomethylthio)benzene,        1,2,4-tris(mercaptomethylthio)benzene,        1,3,5-tris(mercaptomethylthio)benzene,        1,2,3-tris(mercaptoethylthio)benzene,        1,2,4-tris(mercaptoethylthio)benzene, and        1,3,5-tris(mercaptoethylthio)benzene, and ring-alkylated        derivatives of these;    -   aliphatic polythiol compounds containing a sulfur atom other        than in the mercapto group such as bis(mercaptomethyl) sulfide,        bis(mercaptoethyl)sulfide, bis(mercaptopropyl) sulfide,        bis(2-mercaptoethylthio)methane,        bis(3-mercaptopropylthio)methane,        1,2-bis(2-mercaptoethylthio)ethane,        1,2-bis(3-mercaptopropyl)ethane,        1,3-bis(2-mercaptoethylthio)propane,        1,3-bis(3-mercaptopropylthio)propane,        1,2,3-tris(2-mercaptoethylthio)propane,        1,2,3-tris(3-mercaptopropylthio)propane,        1,2-bis[(2-mercaptoethyl)thio]-3-mercaptopropane,        4,8-dimercaptomethyl-1,11-mercapto-3,6,9-trithiaundecane,        4,7-dimercaptomethyl-1,11-mercapto-3,6,9-trithiaundecane,        5,7-dimercaptomethyl-1,11-mercapto-3,6,9-trithiaundecane,        tetrakis(2-mercaptoethylthiomethyl)methane,        tetrakis(3-mercaptopropylthiomethyl)methane,        bis(2,3-dimercaptopropyl)sulfide,        bis(1,3-dimercaptopropyl)sulfide, 2,5-dimercapto-1,4-dithiane,        2,5-dimercaptomethyl-1,4-dithiane,        2,5-dimercaptomethyl-2,5-dimethyl-1,4-dithiane,        bis(mercaptoethyl)disulfide, bis(mercaptopropyl)disulfide, and        esters of thioglycolates and mercaptopropionates of these;    -   hydroxymethyl sulfide bis(2-mercaptoacetate), hydroxymethyl        sulfide bis(3-mercaptopropionate), hydroxyethyl sulfide        bis(2-mercaptoacetate), hydroxyethyl sulfide        bis(3-mercaptopropionate), hydroxypropyl sulfide        bis(2-mercaptoacetate), hydroxypropyl sulfide        bis(3-mercaptopropionate), hydroxymethyl disulfide        bis(2-mercaptoacetate), hydroxymethyl disulfide        bis(3-mercaptopropionate), hydroxyethyl disulfide        bis(2-mercaptoacetate), hydroxyethyl disulfide        bis(3-mercaptopropionate), hydroxypropyl disulfide        bis(2-mercaptoacetate), hydroxypropyl disulfide        bis(3-mercaptopropionate), 2-mercaptoethylether        bis(2-mercaptoacetate), 2-mercaptoethylether        bis(3-mercaptopropionate), 1,4-dithiane-2,5-diol        bis(2-mercaptoacetate), 1,4-dithiane-2,5-diol        bis(3-mercaptopropionate), bis(2-mercaptoethyl)thiodiglycolate,        bis(2-mercaptoethyl)thiodipropionate, bis(2-mercaptoethyl)        4,4-thiodibutylate, bis(2-mercaptoethyl) dithiodiglycolate,        bis(2-mercaptoethyl) dithiodipropionate, bis(2-mercaptoethyl)        4,4-dithiodibutylate, bis(2,3-dimercaptopropyl)thiodiglycolate,        bis(2,3-dimercaptopropyl) thiodipropionate,        bis(2,3-dimercaptopropyl) dithioglycolate, and        bis(2,3-dimercaptopropyl) dithiodipropionate;    -   heterocyclic compounds containing sulfur atoms other than in the        mercapto groups such as 3,4-thiophenedithiol, and        2,5-dimercapto-1,3,4-thiadiazole; and compounds containing        hydroxyl groups and mercapto groups, such as 2-mercaptoethanol,        3-mercapto-1,2-propanediol, glycerin di(mercaptoacetate),        1-hydroxy-4-mercaptocyclohexane, 2,4-dimercaptophenol,        2-mercaptohydroquinone, 4-mercaptophenol,        3,4-dimercapto-2-propanol, 1,3-dimercapto-2-propanol,        2,3-dimercapto-1-propanol, 1,2-dimercapto-1,3-butanediol,        pentaerythritol tris(3-mercaptopropionate), pentaerythritol        mono(3-mercaptopropionate), pentaerythritol        bis(3-mercaptopropionate), pentaerythritol tris(thioglycolate),        dipentaerythritol pentakis(3-mercaptopropionate),        hydroxymethyl-tris(mercaptoethylthiomethyl)methane, and        1-hydroxyethylthio-3-mercaptoethylthiobenzene. These thiol        compounds may be substituted with halogen such as chlorine or        bromine.

Compounds having at least two iso(thio)cyanato groups used in thepresent invention are not particularly limited. Specific examplesthereof include aliphatic polyisocyanate compounds such as hexamethylenediisocyanate, 2,2-dimethylpentane diisocyanate, 2,2,4-trimethylhexanediisocyanate, butene diisocyanate, 1,3-butadiene-1,4-diisocyanate,2,4,4-trimethylhexamethylene diisocyanate, 1,6,11-undecanetriisocyanate, 1,3,6-hexamethylene triisocyanate,1,8-diisocyanato-4-isocyanatomethyloctane,bis(isocyanatoethyl)carbonate, bis(isocyanatoethyl)ether, lysinediisocyanate methyl ester, lysine triisocyanate, xylylene diisocyanate,bis(isocyanatoethyl)benzene, bis(isocyanatopropyl)benzene,α,α,α′,α′-tetramethylxylylene diisocyanate, bis(isocyanatobutyl)benzene,bis(isocyanatomethyl)naphthalene, bis(isocyanatomethylphenyl)ether,bis(isocyanatoethyl) phthalate, and 2,6-di(isocyanatomethyl)furan;

-   -   alicyclic polyisocyanate compounds such as isophorone        diisocyanate, bis(isocyanatomethyl)cyclohexane, cyclohexane        diisocyanate, methylcyclohexane diisocyanate, 4,4′-methylene        bis(cyclohexylisocyanate), 4,4′-methylene        bis(2-methylcyclohexylisocyanate),        2,5-bis(isocyanatomethyl)bicyclo-[2,2,1]-heptane,        2,6-bis(isocyanatomethyl)bicyclo-[2,2,1]-heptane,        3,8-bis(isocyanatomethyl)tricyclodecane,        3,9-bis(isocyanatomethyl)tricyclodecane,        4,8-bis(isocyanatomethyl)tricyclodecane, and        4,9-bis(isocyanatomethyl)tricyclodecane;    -   aromatic polyisocyanate compounds such as        1,2-diisocyanatobenzene, 1,3-diisocyanatobenzene,        1,4-diisocyanatobenzene, 2,4-diisocyanatotoluene, ethylphenylene        diisocyanate, isopropylphenylene diisocyanate, dimethylphenylene        diisocyanate, diethylphenylene diisocyanate,        diisopropylphenylene diisocyanate, trimethylbenzene        triisocyanate, benzene triisocyanate, biphenyl diisocyanate,        toluidine diisocyanate, 4,4′-methylene bis(phenylisocyanate),        4,4′-methylene bis(2-methylphenyl isocyanate),        bibenzyl-4,4′-diisocyanate, and bis(isocyanatophenyl)ethylene;    -   sulfur-containing aliphatic isocyanate compounds such as        bis(isocyanatomethyl)sulfide, bis(isocyanatoethyl) sulfide,        bis(isocyanatopropyl)sulfide, bis(isocyanatohexyl) sulfide,        bis(isocyanatomethyl)sulfone, bis(isocyanatomethyl)disulfide,        bis(isocyanatoethyl) disulfide, bis(isocyanatopropyl)disulfide,        bis(isocyanatomethylthio)methane,        bis(isocyanatoethylthio)methane, bis(isocyanatoethylthio)ethane,        bis(isocyanatomethylthio)ethane,        1,5-diisocyanato-2-isocyanatomethyl-3-thiapentane,        1,2,3-tris(isocyanatomethylthio)propane,        1,2,3-tris(isocyanatoethylthio)propane,        3,5-dithia-1,2,6,7-heptane tetraisocyanate,        2,6-diisocyanatomethyl-3,5-dithia-1,7-heptane diisocyanate,        2,5-diisocyanate methyl thiophene, and        4-isocyanatoethylthio-2,6-dithia-1,8-octane diisocyanate;    -   aromatic sulfide-series isocyanate compounds such as        2-isocyanatophenyl-4-isocyanatophenyl sulfide,        bis(4-isocyanatophenyl)sulfide, and        bis(4-isocyanatomethylphenyl) sulfide;    -   aromatic disulfide-series isocyanate compounds such as        bis(4-isocyanatophenyl)disulfide,        bis(2-methyl-5-isocyanatophenyl)disulfide,        bis(3-methyl-5-isocyanatophenyl)disulfide,        bis(3-methyl-6-isocyanatophenyl)disulfide,        bis(4-methyl-5-isocyanatophenyl)disulfide,        bis(3-methoxy-4-isocyanatophenyl)disulfide, and        bis(4-methoxy-3-isocyanatophenyl)disulfide;    -   sulfur-containing alicyclic compounds such as 2,5-diisocyanato        tetrahydrothiophene, 2,5-diisocyanato methyl        tetrahydrothiophene, 3,4-diisocyanatomethyl tetrahydrothiophene,        2,5-diisocyanato-1,4-dithiane, 2,5-diisocyanato        methyl-1,4-dithiane, 4,5-diisocyanato-1,3-dithiolane,        4,5-bis(isocyanatomethyl)-1,3-dithiolane, and        4,5-diisocyanatomethyl-2-methyl-1,3-dithiolane;    -   aliphatic isothiocyanate compounds such as        1,2-diisothiocyanatoethane and 1,6-diisothiocyanatohexane;        alicyclic isothiocyanate compounds such as cyclohexane        diisocyanate; aromatic isotyiocyanate compounds such as        1,2-diisothiocyanatobenzene, 1,3-diisothiocyanatobenzene,        1,4-diisothiocyanatobenzene, 2,4-diisothiocyanatotoluene,        2,5-diisothiocyanato-m-xylene, 4,4′-diisothiocyanatobiphenyl,        4,4′-methylene bis(phenylisothiocyanate), 4,4′-methylene        bis(2-methylphenyl isothiocyanate), 4,4′-methylene        bis(3-methylphenyl isothiocyanate),        4,4′-isopropylidenebis(phenylisothiocyanate),        4,4′-diisothiocyanatobenzophenone,        4,4′-diisothiocyanato-3,3′-dimethylbenzophenone, and        bis(4-isothiocyanatophenyl)ether;    -   carbonyl isothiocyanate compounds such as        1,3-benzenedicarbonyldiisothiocyanate,        1,4-benzenedicarbonyldiisothiocyanate, and        (2,2-pyridine)-4,4-dicarbonyl diisothiocyanate;        sulfur-containing aliphatic isothiocyanate compounds such as        thiobis(3-isothiocyanatopropane),        thiobis(2-isothiocyanatoethane), and        dithiobis(2-isothiocyanatoethane);    -   sulfur-containing aromatic isothiocyanate compounds such as        1-isothiocyanato-4-[(2-isothiocyanato)sulfonyl]benzene,        thiobis(4-isothiocyanatobenzene),        sulfonylbis(4-isothiocyanatobenzene), and        dithiobis(4-isothiocyanatobenzene); sulfur-containing alicyclic        compounds such as 2,5-diisothiocyanatothiophene and        2,5-diisothiocyanato-1,4-dithiane; and    -   compounds containing isocyanato groups and isothiocyanato        groups, such as 1-isocyanato-6-isothiocyanatohexane,        1-isocyanato-4-isothiocyanatocyclohexane,        1-isocyanato-4-isothiocyanatobenzene,        4-methyl-3-isocyanato-1-isocyanatobenzene,        2-isocyanato-4,6-diisothiocyanato-1,3,5-triazine,        4-isocyanatophenyl-4-isothiocyanatophenyl sulfide, and        2-isocyanatoethyl-2-isothiocyanatoethyl disulfide.

These compounds may be substituted with halogen, e.g., chlorine orbromine, alkyl, alkoxy, or nitro. Moreover, these compounds may bemodified with polyalcohol (polymer type), carbodiimide, urea, or biuret.Dimer or trimer reaction products of these compounds may also be used.

These compounds may be used alone or in combination.

The polymerizable composition of the present invention may contain aresin modifier to modify the monomer system or the resin, i.e., toadjust the optical properties, such as refractive index of the resin,various physical properties, such as impact resistance and specificgravity, the viscosity of the polymerizable composition, handling ease,and the like.

Moreover, as in any conventional forming process, in order to cure thepolymerizable composition of the present invention, various substancessuch as a chain extender, a cross-linker, a photostabilizer, a UVabsorber, an antioxidant, an antiyellowing agent, a bluing agent, anoil-soluble dye, and a filler, may be added as required.

In order to achieve a target reaction rate, an adequate conventionalreaction catalyst may be added. Preferable examples of the catalystinclude urethane reaction catalysts such as tin compounds, e.g.,dibutyltin dilaurate, dibutyltin dichloride, dimethyltin dichloride, andthe like, and amine compounds such as tertiary amine. These catalystsmay be used alone or in combination.

In general, the resin of the present invention is produced by moldinjection polymerization. In particular, additives such as a catalyst, aUV absorber, and an internal mold release agent are blended into atarget monomer in advance to prepare a mixture. The mixture may beprepared by any of the following methods: (1) adding the thiol componentto a premix solution of additives in the isocyanate component; (2)adding the isocyanate component to a premix solution of additives in thethiol component; (3) dissolving the additives in a mixture of theisocyanate component and the thiol component; and (4) adding a mixtureof the isocyanate component and the thiol component to ahigh-concentration master solution of the additives in the isocyanatecomponent or the thiol component.

The resulting mixture was degassed by an adequate method, if necessary.Subsequently, the mixture is injected into a mold constituted from twoglass plates and tapes or gaskets to carry out polymerization. Theinjection method is not particularly limited. Preferably, the viscosityof the monomer mixture is 20 to 1,000 mPa·s.

The polymerization conditions significantly vary according to the typeand/or amount of the monomer and/or catalyst employed, the shape of themold, and the like; hence, the polymerization conditions are notparticularly limited. Thermal polymerization is performed at atemperature of −20 to 200° C. for 1 to 100 hours.

The resin of the invention produced as above is colorless andtransparent, exhibits superior mechanical properties, and is suitablefor use in optical elements, such as plastic lenses, prisms, opticalfibers, information recording boards, filters, light-emitting diodes,and the like.

In order to improve lenses made from the optical resin of the presentinvention, i.e., to provide antireflection properties, high hardness,high wear resistance, high chemical resistance, high defoggingproperties, fashionable tastes, and the like to the lenses, the lensesmay be subjected to physical and/or chemical treatment, if necessary.Examples of such treatment include surface polishing, antistatictreatment, hard coat treatment, non-reflecting coating treatment, anddyeing treatment. In dyeing treatment, a hot water bath containingdispersed dye is normally used; alternatively, a dyebath containingcarrier, such as benzyl alcohol, that improves dyeing rate and dyeingdensity may be used.

EXAMPLES

The present invention will now be specifically described by way ofexamples.

The physical properties of the resin prepared by the polymerization wereevaluated by the following methods.

Refractive Index (ne) and Abbe Number (νe): measured with a Pulfrich'srefractometer at 20° C.

Heat resistance: Tg was measured by TMA penetration method (load: 50 g,probe diameter: 0.5 mm; temperature elevation rate 10° C./min). Impactresistance: Falling weight test was performed according to United StatesFDA standards. In this test, a 16-g steel ball was dropped from a heightof 127 cm onto a lens having a thickness of 1.0 mm at the center. Lensesthat remained unaffected were rated “A”, those that allowed the steelball to penetrate were rated “C”, and those suffered star-shaped crackswere rated “B”.

SYNTHETIC EXAMPLE 1

Into a 3-L round-bottomed flask equipped with a stirrer, a thermometer,and a Dimroth condenser was charged 117.7 g (1.11 mol) of trimethylorthoformate, 200.0 g (2.49 mol) of methanedithiol, 2 L of toluene, and23.6 g (0.124 mol) of p-toluenesulfonic acid. The resulting mixture wasstirred at 20° C. for 43 hours. The resulting reaction solution waswashed several times with water. After performing solvent extraction ofthe organic layer to remove toluene and low-boiling-point components,the resulting mixture was filtered with a 3-μm Teflon filter to obtain122.5 g of a polythiol compound mixture (hereinafter, simply “polythiolcompound A”).

Three peaks were observed by gel permeation chromatography (GPC)(columns: 7.8 mm×300 mm, G1000HXL manufactured by Tosoh Corporation;eluent: THF) of the polythiol compound A, and the peak area ratio was18:29:53. Among these three components, two components with lowermolecular weight were batched off by means of liquid chromatography andwere identified as tris(mercaptomethylthio)methane (hereinafter TMMTM)and 1,1,5,5-tetrakis(mercaptomethylthio)-2,4-dithiapentane (hereinafterTMMTDTP). Analysis results of these two compounds are shown below.Moreover, the molecular weight of the remaining one component wascalculated from the GPC analysis results based on these two components.The number-average molecular weight of the remaining one component was585, and the weight-average molecular weight was 589. These resultsrevealed that this component wasbis(4,4-bis(mercaptomethylthio)-1,3-dithiabutyl)(mercaptomethylthio)methane(molecular weight: 591).

The mercapto equivalent of the polythiol compound A per unit mass(hereinafter “SHV”) was calculated from the peak area ratio of GPC. TheSHV was 10.6 meq/g.

i) TMMTM

¹H-NMR δ(CDCl₃): 2.23 (t, 3H), 3.85 (d, 6H), 5.57 (s, 1H)

13C-NMR δ(CDCl₃): 28.1, 52.7

FT-IR: 2540 cm⁻¹

ii) TMMTDTP

¹H-NMR δ(CDCl₃): 2.22 (t, 4H), 3.86 (d, 8H), 4.08 (s, 2H), 5.57 (s, 2H)

13C-NMR δ(CDCl₃): 28.1, 35.65, 52.7

FT-IR: 2540 cm⁻¹

EXAMPLE 1

In 47.2 g of xylylene diisocyanate were dissolved 10 mg of dibutyltindichloride, i.e., the catalyst, 100 mg of Zelec UN (trade name, acidicalkyl phosphoric ester manufactured by Stepan Company), i.e., theinternal mold release agent, and 50 mg of Viosorb 583 (trade name,manufactured by Kyodo Chemical Co., Ltd.), i.e., the UV absorber, toprepare a solution. Into the solution was added 52.8 g of the polythiolcompound A produced in SYNTHETIC EXAMPLE 1, and the resulting mixturewas thoroughly stirred to prepare a monomer mixture. The molar ratio ofthe mercapto group to the isocyanato group in the monomer mixture wasSH/NCO=1.12 at this stage. The monomer mixture was degassed for one hourat 0.6 kPa. A moiety of the mixture was then injected into a lens mold,gradually heated from 40° C. to 120° C., and cured over 21 hours. Aftercooling, the produced lens was released from the glass mold. The lenswas colorless and transparent. Using a slide projector, light wastransmitted through the lens in a darkroom, and no muddiness wasobserved in the lens. As for the optical properties, the refractiveindex (ne) was 1.704, and the Abbe number (νe) was 30. As for the heatresistance, the Tg point was 94.3° C., which was satisfactory. Theimpact resistance was “A”.

SYNTHETIC EXAMPLE 2

Into a 2-L flask equipped with a bottom outlet cock, a stirrer, athermometer, a distillation column, and a capillary for introducingnitrogen was charged 164.2 g (1 mol) of 1,1,3,3-tetramethoxypropane,488.8 g (4 mol) of acetyl mercaptomethyl mercaptan, and 7.6 g (0.04 mol)of p-toluenesulfonic acid to prepare a mixture. The mixture was heatedto 40° C. with stirring at a degree of vacuum of 1 kPa or less. Theheating was continued for 18 hours until distillation of methanol cameto a halt. After cooling, the vacuum was released, and a condenser wasinstalled to replace the distillation column. To the resulting mixturewas added 400 ml of methanol, 400 ml of chloroform, and 200 ml of 36% ofhydrochloric acid. The resulting mixture was heated to 60° C. to performalcoholysis so as to produce a target compound, i.e.,1,1,3,3-tetrakis(mercaptomethylthio)propane (hereinafter, “polythiolcompound B”).

Adequate amounts of water and chloroform were added to the mixture toperform liquid separation, and the chloroform layer was washed withwater several times. Solvent extraction was performed to removechloroform and low-boiling-point components; subsequently, the mixturewas filtered with a 3-μm Teflon filter to obtain 340.0 g of thepolythiol compound B. According to the LC analysis of the polythiolcompound B, two components other than the polythiol compound B weredetected (9.8% and 9.8% based on chromatogram areal ratio). Thesecomponents were purified by preparative LC and analyzed. They were foundto be 4,6-bis(mercaptomethylthio)-1,3-dithiane and2-(2,2-bis(mercaptomethylthio)ethyl)-1,3-dithietane. The analysisresults are shown below.

The SHV of the polythiol compound B (containing the above-described twoby-product components) was calculated from the chromatogram area ratiobased on LC. The SHV was 10.5 meq/g.

iii) 1,1,3,3-tetrakis(mercaptomethylthio)propane

1H-NMR δ(CDCl₃): 2.18 (t, 4H), 2.49 (t, 2H), 3.78-3.90 (m, 8H), 4.64 (t,2H)

13C-NMR δ(CDCl₃): 26.7, 41.3, 48.7

FT-IR: 2538 cm⁻¹

MS: m/z=356(M+)

iv) 4,6-bis(mercaptomethylthio)-1,3-dithiane

1H-NMR δ(CDCl₃): 2.02 (t, 2H), 2.56 (t, 2H), 3.77-3.91 (m, 4H), 3.97 (s,2H), 4.66 (t, 2H)

13C-NMR δ(CDCl₃): 27.1, 28.8, 38.1, 44.6

FT-IR: 2538 cm⁻¹

MS: m/z=276(M+)

vi) 2-(2,2-bis(mercaptomethylthio)ethyl)-1,3-dithietane

1H-NMR δ(CDCl₃): 2.03 (t, 2H), 2.13-2.21 (m, 1H), 2.75-2.80 (m, 1H),3.79-3.84 (m, 1H), 3.90-3.96 (m, 3H), 4.32-4.35 (m, 2H)

13C-NMR δ(CDCl₃): 27.2, 32.3, 38.9, 46.2

FT-IR: 2538 cm-1

MS: m/z=276(M+)

EXAMPLE 2

In 45.6 g of xylylene diisocyanate were dissolved 30 mg of dibutyltindichloride, i.e., the catalyst, 150 mg of Zelec UN (trade name, acidicalkyl phosphoric ester manufactured by Stepan Company), i.e., theinternal mold release agent, and 50 mg of Viosorb 583 (trade name,manufactured by Kyodo Chemical Co., Ltd.), i.e., the UV absorber, toprepare a solution. Into the solution was added 54.4 g of the polythiolcompound B produced in SYNTHETIC EXAMPLE 2, and the resulting mixturewas thoroughly stirred to prepare a monomer mixture. The molar ratio ofthe mercapto group to the isocyanato group in the monomer mixture wasSH/NCO=1.18 at this stage. The monomer mixture was degassed for one hourat 0.6 kPa. A moiety of the mixture was then injected into a lens mold,gradually heated from 40° C. to 130° C., and cured over 20 hours. Aftercooling, the produced lens was released from the glass mold. The lenswas colorless and transparent. Using a slide projector, light wastransmitted through the lens in a darkroom, and no muddiness wasobserved in the lens. As for the optical properties, the refractiveindex (ne) was 1.693, and the Abbe number (νe) was 30. As for the heatresistance, the Tg point was 99.5° C., which was satisfactory. Theimpact resistance was “A”.

SYNTHETIC EXAMPLE 3

Into a 2-L flask equipped with a bottom outlet cock, a stirrer, athermometer, a distillation column, and a capillary for introducingnitrogen was charged 164.2: g (1 mol) of 1,1,3,3-tetramethoxypropane and488.8 g (4 mol) of acetyl mercaptomethyl mercaptan. The resultingmixture was cooled to 5° C. Into the mixture, 7.6 g (0.04 mol) ofp-toluenesulfonic acid was added. The resulting mixture was heated to50° C. with stirring over four hours while the degree of vacuum wasmaintained at 2.67 kPa. The heating was continued for about five hoursafter the temperature was elevated to 50° C. until distillation ofmethanol came to a halt. After cooling, the vacuum was released, and acondenser was installed to replace the distillation column. Into theresulting mixture was added 176.9 g of methanol, 353.7 g of toluene, and30.4 g (0.16 mol) of p-toluenesulfonic acid. The resulting mixture washeated to 60° C. to perform alcoholysis so as to form the polythiolcompound B.

The toluene layer was washed with an adequate amount of water severaltimes. After performing solvent extraction to remove toluene andlow-boiling-point components, the mixture was filtered with 1-μm Teflonfilter to obtain 340.0 g of polythiol compound B. As in SYNTHETICEXAMPLE 2, two components other than the polythiol compound B weredetected in the LC analysis. These two components were the same as inSYNTHETIC EXAMPLE 2.

The SHV of the polythiol compound B (containing the above-described twoby-product components) was 9.8 meq/g.

EXAMPLE 3

In 44.3 g of xylylene diisocyanate were dissolved 20 mg of dibutyltindichloride, i.e., the catalyst, 100 mg of Zelec UN (trade name, acidicalkyl phosphoric ester manufactured by Stepan Company), i.e., theinternal mold release agent, and 50 mg of Viosorb 583 (trade name,manufactured by Kyodo Chemical Co., Ltd.), i.e., the UV absorber, toprepare a solution. Into the solution was added 55.7 g of the polythiolcompound B produced in SYNTHETIC EXAMPLE 3, and the resulting mixturewas thoroughly stirred to prepare a monomer mixture. The molar ratio ofthe mercapto group to the isocyanato group in the monomer mixture wasSH/NCO=1.16 at this stage. The monomer mixture was degassed for one hourat 0.6 kPa and was filtered with 1-μm Teflon filter. A moiety of themixture was then injected into a lens mold, gradually heated from 40° C.to 130° C., and cured over 20 hours. After cooling, the produced lenswas released from the glass mold. The lens was colorless andtransparent. Using a slide projector, light was transmitted through thelens in a darkroom, and no muddiness was observed in the lens. As forthe optical properties, the refractive index (ne) was 1.695, and theAbbe number (νe) was 30. As for the heat resistance, the Tg point was100.1° C., which was satisfactory. The impact resistance was “A”.

SYNTHETIC EXAMPLE 4

The same steps were performed as in SYNTHETIC EXAMPLE 3 except that thedegree of vacuum was maintained at 4.00 kPa.

The SHV of the polythiol compound B produced was 9.5 meq/g.

EXAMPLE 4

The same steps were performed as in EXAMPLE 3 except that the polythiolcompound B produced in SYNTHETIC EXAMPLE 4 was used. The molar ratio ofthe mercapto group to the isocyanato group in the monomer mixture wasSH/NCO=1.13. The obtained lens was colorless and transparent. Using aslide projector, light was transmitted through the lens in a darkroom,and no muddiness was observed in the lens. As for the opticalproperties, the refractive index (ne) was 1.696, and the Abbe number(νe) was 30. As for the heat resistance, the Tg point was 100.0° C.,which was satisfactory. The impact resistance was “A”.

SYNTHETIC EXAMPLE 5

The same steps were performed as in SYNTHETIC EXAMPLE 3 except that thedegree of vacuum was maintained at 5.33 kPa.

The SHV of the polythiol compound B produced was 9.3 meq/g.

EXAMPLE 5

The same steps were performed as in EXAMPLE 3 except that the polythiolcompound B produced in SYNTHETIC EXAMPLE 5 was used. The molar ratio ofthe mercapto group to the isocyanato group in the monomer mixture wasSH/NCO=1.09. The obtained lens was colorless and transparent. Using aslide projector, light was transmitted through the lens in a darkroom,and no muddiness was observed in the lens. As for the opticalproperties, the refractive index (ne) was 1.696, and the Abbe number(νe) was 30. As for the heat resistance, the Tg point was 103.1° C.,which was satisfactory. The impact resistance was “A”.

COMPARATIVE EXAMPLE 1

Using 49.8 g of xylylene diisocyanate and 50.2 g of the polythiolcompound A, the polymerization was performed as in EXAMPLE 1 to producea lens. The molar ratio of the mercapto group to the isocyanato group inthe monomer mixture was SHINCO=1.01. As for the optical properties, therefractive index (ne) was 1.700, and the Abbe number (νe) was 30. As forthe heat resistance, the Tg point was 96.0° C. The impact resistance was“A”.

COMPARATIVE EXAMPLE 2

Using 24.9 g of xylylene diisocyanate and 75.1 g of polythiol compoundA, the polymerization was performed as in EXAMPLE 1. The produced resinwas rubbery in room temperature and had poor heat resistance. Moreover,the molar ratio of the mercapto group to isocyanato group in the monomermixture was SH/NCO=3.004.

COMPARATIVE EXAMPLE 3

Using 50.0 g of xylylene diisocyanate and 50.0 g of the polythiolcompound B produced in SYNTHETIC EXAMPLE 2, the polymerization wasperformed as in EXAMPLE 2 to produce a lens. The molar ratio of themercapto group to the isocyanato group in the monomer mixture wasSH/NCO=0.99. As for the optical properties, the refractive index (ne)was 1.688, and the Abbe number (νe) was 30. As for the heat resistance,the Tg point was 106.0° C. The impact resistance was “A”.

COMPARATIVE EXAMPLE 4

Using 24.7 g of xylylene diisocyanate and 75.3 g of the polythiolcompound B produced in SYNTHETIC EXAMPLE 2, the polymerization wasperformed as in EXAMPLE 2. The produced resin was rubbery in roomtemperature and had poor heat resistance. The molar ratio of themercapto group to the isocyanato group in the monomer mixture wasSH/NCO=3.01.

COMPARATIVE EXAMPLE 5

Using 48.0 g of xylylene diisocyanate and 52.0 g of the polythiolcompound B produced in SYNTHETIC EXAMPLE 3, the polymerization wasperformed as in EXAMPLE 2 to produce a lens. The molar ratio of themercapto group to the isocyanato group in the monomer mixture wasSH/NCO=1.00. As for the optical properties, the refractive index (ne)was 1.690, and the Abbe number (νe) was 30. As for the heat resistance,the Tg point was 106.3° C. The impact resistance was “A”.

COMPARATIVE EXAMPLE 6

Using 47.3 g of xylylene diisocyanate and 52.7 g of the polythiolcompound B produced in SYNTHETIC EXAMPLE 4, the polymerization wasperformed as in EXAMPLE 3 to produce a lens. The molar ratio of themercapto group to the isocyanato group in the monomer mixture wasSH/NCO=1.00. As for the optical properties, the refractive index (ne)was 1.690, and the Abbe number (νe) was 30. As for the heat resistance,the Tg point was 106.3° C. The impact resistance was “A”.

COMPARATIVE EXAMPLE 7

Using 48.0 g of xylylene diisocyanate and 52.0 g of the polythiolcompound B produced in SYNTHETIC EXAMPLE 4, the polymerization wasperformed as in EXAMPLE 4 to produce a lens. The molar ratio of themercapto group to the isocyanato group in the monomer mixture wasSH/NCO=1.00. As for the optical properties, the refractive index (ne)was 1.690, and the Abbe number (νe) was 30. As for the heat resistance,the Tg point was 109.2° C. The impact resistance was “A”.

COMPARATIVE EXAMPLE 8

In 52.0 g of xylylene diisocyanate were dissolved 10 mg of dibutyltindichloride, i.e., the catalyst, 100 mg of Zelec UN (trade name, acidicalkyl phosphoric ester manufactured by Stepan Company), i.e., theinternal mold release agent, and 50 mg of Viosorb 583 (trade name,manufactured by Kyodo Chemical Co., Ltd.), i.e., the UV absorber, toprepare a solution. Into the solution was added 48.0 g of4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane (hereinafter, the“polythiol compound C”), and the resulting mixture was thoroughly mixedto prepare a monomer mixture. The molar ratio of the mercapto group tothe isocyanato group in the monomer mixture was SH/NCO=1.00 at thisstage. The monomer mixture was degassed for one hour at 0.6 kPa. Amoiety of the mixture was then injected into a lens mold, graduallyheated from 40° C. to 120° C., and cured over 20 hours. After cooling,the produced lens was released from the glass mold. The lens wascolorless and transparent. Using a slide projector, light wastransmitted through the lens in a darkroom, and no muddiness wasobserved in the lens. As for the optical properties, the refractiveindex (ne) was 1.660, and the Abbe number (νe) was 32. As for the heatresistance, the Tg point was 85.0° C. The impact resistance was “A”.

COMPARATIVE EXAMPLE 9

Using 48.5 g of xylylene diisocyanate and 51.5 g of the polythiolcompound C, the polymerization was performed as in COMPARATIVE EXAMPLE 5to produce a lens. The molar ratio of the mercapto group to theisocyanato group in the monomer mixture was SH/NCO=1.15. The lens wascolorless and transparent. Using a slide projector, light wastransmitted through the lens in a darkroom, and no muddiness wasobserved in the lens. As for the optical properties, the refractiveindex (ne) was 1.663, and the Abbe number (νe) was 32. As for the heatresistance, the Tg point was 62.1° C. The impact resistance was “A”.

COMPARATIVE EXAMPLE 10

In 50.7 g of xylylene diisocyanate were dissolved 10 mg of dibutyltindichloride, i.e., the catalyst, 100 mg of Zelec UN (trade name, acidicalkyl phosphoric ester manufactured by Stepan Company), i.e., theinternal mold release agent, and 50 mg of Viosorb 583 (trade name,manufactured by Kyodo Chemical Co., Ltd.), i.e., the UV absorber, toprepare a solution. Into the solution was added 49.3 g of4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane (hereinafter,the “polythiol compound D”), and the resulting mixture was thoroughlymixed to prepare a monomer mixture. The molar ratio of the mercaptogroup to the isocyanato group in the monomer mixture was SH/NCO=1.00.The monomer mixture was degassed for one hour at 0.6 kPa. A moiety ofthe mixture was then injected into a lens mold, gradually heated from40° C. to 120° C., and cured over 20 hours. After cooling, the producedlens was released from the glass mold. The lens was colorless andtransparent. Using a slide projector, light was transmitted through thelens in a darkroom, and no muddiness was observed in the lens. As forthe optical properties, the refractive index (ne) was 1.667, and theAbbe number (νe) was 31. As for the heat resistance, the Tg point was100.2° C. The impact resistance was “A”.

COMPARATIVE EXAMPLE 11

Using 46.1 g of xylylene diisocyanate and 53.9 g of the polythiolcompound D, the polymerization was performed as in COMPARATIVE EXAMPLE 7to produce a lens. The molar ratio of the mercapto group to theisocyanato group in the monomer mixture was SH/NCO=1.20. The lens wascolorless and transparent. Using a slide projector, light wastransmitted through the lens in a darkroom, and no muddiness wasobserved in the lens. As for the optical properties, the refractiveindex (ne) was 1.670, and the Abbe number (νe) was 32. As for the heatresistance, the Tg point was 82.1° C. The impact resistance was “A”.

The above-described results are summarized in Table 1. In Table 1, Δneand ΔTg denote, respectively, the differences in refractive index (ne)and heat resistance (Tg) between when the molar ratio of the mercaptogroup to the isocyanato group (SH/NCO) is greater than 1.01 and when themolar ratio of the mercapto group to the isocyanato group (SH/NCO) isnot more than 1.0. The larger Δne/ΔTg, the better the heat resistanceand the higher the refractive index. The resin made from thepolymerizable composition containing the polythiol of the presentinvention exhibited Δne/ΔTg larger than those of COMPARATIVE EXAMPLESthat use conventional polythiols. In other words, the refractive indexof the resin improved dramatically. Meanwhile, a decrease in heatresistance was small, and satisfactory impact resistance was maintained.In COMPARATIVE EXAMPLES 5, 6, 7, and 8, the heat resistance drasticallydegraded as the molar ratio of the mercapto group to the isocyanatogroup in the polymerizable composition exceeded 1.0.

Regarding the heat resistance of the resin, the heat resistanttemperature of the resin of COMPARATIVE EXAMPLE 5, i.e., a typicalwidespread thiourethane optical resin, was 85.0° C.; accordingly, theresin can be put to practical application if the resin has higher heatresistant temperature than this temperature. Therefore, the resin ofeach EXAMPLE has sufficient heat resistance. The heat resistance of theresins of COMPARATIVE EXAMPLES 6 and 8 is insufficient. Note that, asshown in COMPARATIVE EXAMPLES 2 and 4, the resin becomes rubbery andexhibits poor heat resistance when the ratio of the mercapto group tothe isocyanato group exceeds 3.0. Although the above-described EXAMPLESdescribe compounds having isocyanato groups, the same results can beobtained by using compounds having isothiocyanato groups. TABLE 1 HeatIm- SH/NCO Refractive resis- pact Molar index tance resis- Δ ne/Tg Thiolratio (ne) ° C. tance (×10⁻³) Polythiol Ex. 1 1.12 1.704 94.3 A 2.11compound A C.Ex. 1 1.00 1.700 96.2 A Poythiol Ex. 2 1.18 1.693 99.5 A0.77 compound B C.Ex. 3 0.99 1.688 106.0 A Polythiol Ex. 3 1.16 1.695100.1 A 0.85 compound B C.Ex. 5 1.00 1.690 106.0 A Polythiol Ex. 4 1.131.696 100.0 A 0.95 compound B C.Ex. 6 1.00 1.690 106.3 A Polythiol Ex. 51.09 1.696 103.1 A 0.98 compound B C.Ex. 7 1.00 1.690 109.2 A PolythiolC.Ex. 9 1.15 1.663 62.1 A 0.13 compound C C.Ex. 8 1.00 1.660 85.0 APolythiol C.Ex. 11 1.20 1.670 82.1 A 0.17 compound D C.Ex. 10 1.00 1.667100.1 A*Ex. = EXAMPLE, C.Ex. = COMPARATIVE EXAMPLE

Industrial Applicability

According to the present invention, the refractive index of the resincan be easily increased while maintaining the heat and impactresistance.

1. A polymerizable composition for making a high-refractive-index resin,the composition containing a polythiol compound having a dithioacetal,dithioketal, orthotrithioformic ester, or orthotetrathiocarbonic esterskeleton, and at least two mercapto groups; and a compound having atleast two iso(thio)cyanato groups, wherein the molar ratio of themercapto group to the iso(thio)cyanato group is greater than 1.0 but notmore than 3.0.
 2. The polymerizable composition according to claim 1,wherein the polythiol compound has a mercaptomethylthio group.
 3. Thepolymerizable composition according to claim 2, wherein the polythiolcompound having the dithioketal or dithioacetal skeleton is representedby General Formula (1)

(wherein R¹ is an aliphatic residue, a heterocyclic residue, or anaromatic residue with a valence of n; R² is a hydrogen atom or analiphatic residue, a heterocyclic residue, or an aromatic residue with avalence of 1; and R³ and R⁴ are each independently an aliphatic residue,a heterocyclic residue, or an aromatic residue with a valence of 1, andR³ and R⁴ may bond to each other to form a ring or each may bond to R³or R⁴ in another set of parentheses to form a ring when n is 2 or more;wherein at least one of R¹, R², R³, and R⁴ must have at least onemercapto group, and m1+(m2+m3+m4)×n≧2, wherein m1, m2, m3, and m4represent the numbers of mercapto group contained in R¹, R², R³, and R⁴,respectively, and n is an integer of 1 or more.)
 4. The polymerizablecomposition according to claim 3, wherein R² in General Formula (1) is ahydrogen atom.
 5. The polymerizable composition according to claim 4,wherein the polythiol compound having the dithioacetal skeleton is atleast one selected from the group consisting of1,1,3,3-tetrakis(mercaptomethylthio)propane,1,1,2,2-tetrakis(mercaptomethylthio)ethane,4,6-bis(mercaptomethylthio)-1,3-dithiane, and2-(2,2-bis(mercaptomethylthio)ethyl)-1,3-dithietane.
 6. Thepolymerizable composition according to claim 2, wherein the polythiolcompound having the orthotrithioformic ester skeleton is represented byGeneral Formula (2)

(wherein R⁵ is an aliphatic residue, a heterocyclic residue, or anaromatic residue with a valence of p; R⁶ and R⁷ are each independentlyan aliphatic residue, a heterocyclic residue, or an aromatic residuewith a valence of 1, and R⁶ and R⁷ may bond to each other to form aring; wherein, at least one of R⁵, R⁶ and R⁷ must have at least onemercapto group, m5+(m6+m7)×p≧2, wherein m5, m6, and m7 represent thenumbers of mercapto group contained in R⁵, R⁶, and R⁷, respectively, andp is an integer of 1 or more.)
 7. The polymerizable compositionaccording to claim 6, wherein R⁶ and R⁷ are each a mercaptomethyl group.8. The polymerizable composition according to claim 7, wherein thepolythiol compound represented by General Formula (2) is at least oneselected from the group consisting of tris(mercaptomethylthio)methane,1,1,5,5-tetrakis(mercaptomethylthio)-2,4-dithiapentane, andbis(4,4-bis(mercaptomethylthio)-1,3-dithiabutyl)(mercaptomethylthio)methane.9. The polymerizable composition according to claim 2, wherein thepolythiol compound having the orthotetrathiocarbonic ester skeleton isrepresented by General Formula (3)

(wherein R⁸, R⁹, R¹⁰, and R¹¹ are each independently an aliphaticresidue, a heterocyclic residue, or an aromatic residue and may eachbond with one of other residues to form a ring; wherein at least one ofR⁸, R⁹, R¹⁰, and R¹¹ must contain at least one mercapto group, andm8+m9+m10+m11≧2, wherein m8, m9, m10, and m11 represent the numbers ofmercapto group in R⁸, R⁹, R¹⁰, and R¹¹, respectively.)
 10. A method formaking a resin by curing the polymerizable composition accordingclaim
 1. 11. A resin prepared by curing the polymerizable compositionaccording claim
 1. 12. An optical element comprising the resin accordingto claim
 11. 13. A lens comprising the optical element according toclaim
 12. 14. 4,6-bis(mercaptomethylthio)-1,3-dithiane. 15.2-(2,2-bis(mercaptomethylthio)ethyl)-1,3-dithietane.
 16. Thepolymerizable composition according to claim 1, wherein the polythiolcompound having the dithioketal or dithioacetal skeleton is representedby General Formula (1)

(wherein R¹ is an aliphatic residue, a heterocyclic residue, or anaromatic residue with a valence of n; R² is a hydrogen atom or analiphatic residue, a heterocyclic residue, or an aromatic residue with avalence of 1; and R³ and R⁴ are each independently an aliphatic residue,a heterocyclic residue, or an aromatic residue with a valence of 1, andR³ and R⁴ may bond to each other to form a ring or each may bond to R³or R⁴ in another set of parentheses to form a ring when n is 2 or more;wherein at least one of R¹, R², R³, and R⁴ must have at least onemercapto group, and m1+(m2+m3+m4)×n≧2, wherein m1, m2, m3, and m4represent the numbers of mercapto group contained in R¹, R², R³, and R⁴,respectively, and n is an integer of 1 or more.)
 17. The polymerizablecomposition according to claim 16, wherein R² in General Formula (1) isa hydrogen atom.
 18. The polymerizable composition according to claim17, wherein the polythiol compound having the dithioacetal skeleton isat least one selected from the group consisting of1,1,3,3-tetrakis(mercaptomethylthio)propane,1,1,2,2-tetrakis(mercaptomethylthio)ethane,4,6-bis(mercaptomethylthio)-1,3-dithiane, and2-(2,2-bis(mercaptomethylthio)ethyl)-1,3-dithietane.
 19. Thepolymerizable composition according to claim 1, wherein the polythiolcompound having the orthotrithioformic ester skeleton is represented byGeneral Formula (2)

(wherein R⁵ is an aliphatic residue, a heterocyclic residue, or anaromatic residue with a valence of p; R⁶ and R⁷ are each independentlyan aliphatic residue, a heterocyclic residue, or an aromatic residuewith a valence of 1, and R⁶ and R⁷ may bond to each other to form aring; wherein, at least one of R⁵, R⁶ and R⁷ must have at least onemercapto group, m5+(m6+m7)×p≧2, wherein m5, m6, and m7 represent thenumbers of mercapto group contained in R⁵, R⁶, and R⁷, respectively, andp is an integer of 1 or more.)
 20. The polymerizable compositionaccording to claim 19, wherein R⁶ and R⁷ are each a mercaptomethylgroup.
 21. The polymerizable composition according to claim 20, whereinthe polythiol compound represented by General Formula (2) is at leastone selected from the group consisting oftris(mercaptomethylthio)methane,1,1,5,5-tetrakis(mercaptomethylthio)-2,4-dithiapentane, andbis(4,4-bis(mercaptomethylthio)-1,3-dithiabutyl)(mercaptomethylthio)methane.22. The polymerizable composition according to claim 1, wherein thepolythiol compound having the orthotetrathiocarbonic ester skeleton isrepresented by General Formula (3)

(wherein R⁸, R⁹, R¹⁰, and R¹¹ are each independently an aliphaticresidue, a heterocyclic residue, or an aromatic residue and may eachbond with one of other residues to form a ring; wherein at least one ofR⁸, R⁹, R¹⁰, and R¹¹ must contain at least one mercapto group, andm8+m9+m10+m11≧2, wherein m8, m9, m10, and m11 represent the numbers ofmercapto group in R⁸, R⁹, R¹⁰, and R¹¹, respectively.)